Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-In HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, uses a middle or large-sized battery module having a plurality of battery cells electrically connected to one another because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, the battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, and the manufacturing costs of the pouch-shaped battery are low.
Also, the secondary battery is used as a power source for vehicles or as an emergency power source for relay stations of telecommunication corporations as a result of extension of the application range of the secondary battery. Consequently, fastening means to maintain a compact and stable coupling state of a module case are needed.
However, in a case in which the battery module is constructed using a plurality of battery cells or a plurality of cell modules, each of which includes a predetermined number of battery cells, a plurality of members for mechanical fastening and electrical connection therebetween is generally needed with the result that a process of assembling the mechanical fastening and electrical connection members is very complicated. Furthermore, there is needed a space for coupling, welding, or soldering of the mechanical fastening members with the result that the total size of the battery system is increased.
Meanwhile, a large amount of heat is generated from such a high-power, large-capacity secondary battery during the charge and discharge of the battery. If the heat, generated from a battery module during the charge and discharge of the battery module, is not effectively removed from the battery module, the heat accumulates in the battery module with the result that deterioration of the battery module is accelerated. According to circumstances, the battery module may catch fire or explode. For this reason, a battery pack of high power and large capacity needs a cooling system to cool battery cells mounted in the battery pack.
Each battery module mounted in a middle or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with high integration. In this case, the battery cells are stacked in a state in which the battery cells are arranged at predetermined intervals such that heat generated during the charge and discharge of the battery cells is removed. For example, the battery cells may be sequentially stacked in a state in which the battery cells are arranged at predetermined intervals without using an additional member. Alternatively, in a case in which the battery cells have low mechanical strength, one or more battery cells are mounted in a cartridge, and a plurality of cartridges is stacked to constitute a battery module. Coolant channels are defined between the stacked battery cells or between the stacked battery modules so that heat accumulated between the stacked battery cells or between the stacked battery modules is effectively removed.
In this structure, however, it is necessary to provide a plurality of coolant channels corresponding to the number of the battery cells with the result that the overall size of the battery module is increased.
Also, intervals between the coolant channels are relatively narrowed as a plurality of battery cells is stacked in consideration of the size of the battery module. As a result, design of the cooling structure is complicated. That is, high pressure loss is caused by the coolant channels arranged at intervals narrower than a coolant inlet port with the result that it is difficult to design shapes and positions of the coolant inlet port and a coolant outlet port. Also, a fan may be further provided to prevent such pressure loss. In this case, design may be restricted due to power consumption, fan noise, space or the like.
The increase in size of the battery module and the complexity in structure of the battery module are not preferable in the above regard. Consequently, there is a high necessity for a battery module which is compact, has a fastening structure of excellent stability, and exhibits high cooling efficiency.